In general, an electric vehicle is configured such that power from an overhead line is taken into a power collecting apparatus and an alternating current motor (hereinafter referred to just as an “AC motor”) is driven by a power conversion device, such as an inverter apparatus using the power taken in. The electric vehicle employs what is called a regenerative brake, which obtains a braking force by making the AC motor operate in a regenerative mode when a vehicle is braking. The regenerative power generated at the time of braking is supplied to a load such as another train running nearby the own braking train through the overhead line or a third rail, and is consumed therein.
However, in the case of a low-active line section in which a small number of trains are running early in the morning or at night, there may be a case in which no other trains are nearby the own train (a regenerative load is insufficient), which means that the regenerative power generated by the regenerative brake may not be sufficiently consumed. In a case in which the regenerative power of the own train is larger than the power consumed by the other trains, the overhead line voltage is increased, which means that various types of apparatuses connected to the overhead line may be tripped or damaged by overvoltage.
Therefore, the inverter apparatus mounted in the electric vehicle detects the overhead line voltage (or a voltage corresponding to the overhead line voltage, for example, a filter capacitor voltage on the input side of the inverter apparatus) by a voltage detector. In a case in which the overhead line voltage or the like (such as the overhead line voltage, the filter capacitor voltage) is increased and exceeds a predetermined value, the inverter apparatus performs control such that the regenerative braking force is reduced in order to decrease the regenerative power, and thus prevent the voltage from increasing. In this case, insufficient braking force generated only by the regenerative brake is compensated for by using another brake (an air brake or the like), but because the other brake consumes power by converting electric energy into thermal energy, the utilization efficiency of the electric power is reduced. Therefore, it is desirable that the usage rate of the regenerative braking force itself be increased as much as possible.
With regard to the above-described problems, in the invention disclosed in Patent Literature 1, the regenerative power is temporarily stored in a power storage apparatus, and it is effectively used by being consumed by a load when a train is running or coasting.